1. Field of the Invention
This invention relates to a process for reclaiming and recycling post consumer carpet. More specifically, it relates to a process for reclaiming and recycling the face yarn of post consumer carpet. The reclaimed and recycled face yarn may be used to produce further yarn for both textile and floorcovering applications. The reclaimed and recycled face yarn may also be used to produce articles for other non-yarn related applications such as injection molded articles.
2. The Prior Art
Over the last two decades, carpets for domestic and for institutional use have been increasingly made from synthetic polymeric materials, and a major problem has arisen with respect to disposal of such floorcoverings when they reach the end of their useful life. Disposal of such wastes can be achieved in several ways. Two ways are either by burying in a landfill site or by burning in an incinerator facility. In the United States an estimated 5 billion pounds of carpet waste is dumped into landfills. Landfill sites are becoming increasingly scarce and expensive to use. Recent research has also suggested that landfill sites, located conveniently close to urban areas, are implicated in health problems within local populations. Incineration of waste is also the subject of much environmental disapproval, both by the public and in some scientific circles. Also, the energy recovered from incineration of waste plastics is low, particularly in terms of the volume of such scrap.
Most of the components that make up carpet are potentially recyclable or reusable. Thus, an alternative option to dumping in landfills or incineration, and the most favored option for dealing with waste plastics, is the recycling of these into other materials and/or products. However, this is not a simple option as might be first envisaged. Despite the public perception of “plastic” as being a single term to describe materials which are virtually identical, it is well known in the art that this is not the case, and that different types of plastics do not easily combine together to form a coherent single material. Reprocessing of mixed plastics waste streams, with no sorting of types, or addition of other materials, invariably results in materials of low end value. In many cases the cost of the equipment involved, and the energy expended, cannot be recouped in selling on the product. In order to produce materials of value to the industry from recycled materials, a great deal of expertise has to be applied, and particular waste streams, of known and consistent content, must be available.
Modern carpets generally consist of three major components. Firstly, there is the face yarn, which may be of many different fiber types or mixtures thereof. Secondly, there is a primary backing (to which the yarn is fixed, or into which it is woven), which is most commonly a woven or nonwoven fabric of a polyester or a polyolefin. Thirdly, there is a secondary backing layer. The secondary backing tends to form the majority of the weight of the construct and is typically laminated to the tufted carpet. The secondary backing may be a sheet or foamed material, often containing a high level of coarse particle inorganic mineral fillers. Examples of base materials for the secondary backing are polyolefins, polyurethanes, PVC, bitumen and latex.
Various attempts have been made to recycle carpet scrap without prior separation of the components. JP 60 206 868, to Ikeda Bussan, describes pulverizing the waste carpet, mixing with ethylene-vinyl acetate in approximately 50:50 ratio, and calendaring to form a backing sheet for carpet use. The calendaring is carried out at low temperatures, such that the fiber component does not melt, but is instead merely dispersed through the product. U.S. Pat. No. 5,728,741 to Collins and Aikman claims a similar approach, although in this case the scrap is extruded at high temperature, prior to calendaring, so that all components are molten and are mixed in the melt state. Other patents refer to the recycling of unseparated carpet scrap, but using maleated polyolefins and/or ethylene-vinyl acetate as compatibilizers. See, for example, JP 05 287 139 to Teijin; JP 05 293 828 to Toyota/Mitsubishi; and U.S. Pat. No. 5,719,198 to Lear Corporation. U.S. Pat. No. 5,626,939 to Georgia Tech. takes a low energy approach by mixing well shredded carpet scrap with thermosetting resin precursors, and forming and crosslinking the result mixes into “synthetic wood.” None of the above processes results in a melt spinnable product suitable for making fibers or yarns.
Other inventors have sought to separate the components of scrap carpets prior to recycling same as separate product streams. These mainly involve the chopping, shredding, and granulation of the carpet, followed by separation of the various polymer components via cyclone, hydrocyclone, or varying density liquid flotation baths. See, for example, U.S. Pat. No. 5,230,473 to Hagguist and Hume; U.S. Pat. No. 5,518,188 to JPS Automotive; U.S. Pat. No. 5,535,945 to BASF Corporation; U.S. Pat. No. 5,598,980 to Zimmer A. G.; and U.S. Pat. No. 5,722,603 to AlliedSignal/DSM. Dissolution methods have also been suggested; e.g., U.S. Pat. No. 5,233,021 to Georgia Tech. describes the use of a supercritical fluid approach, in which variation of temperature and pressure is used to sequentially dissolve the various components of the scrap carpet. Another alternative approach, used for carpets containing nylon 6, is the direct recovery of caprolactam from the carpet scrap, as described in U.S. Pat. No. 5,169,870 to BASF corporation, and U.S. Pat. No. 5,668,277 to DSM. Similar efforts have been made for monomer recovery from nylon 66 and mixtures of nylons, for example, U.S. Pat. No. 5,526,694 and U.S. Pat. No. 5,468,900 to E.I. DuPont de Nemours and Company. The recovered monomers from these processes can then be repolymerized to produce polymers for further fiber spinning. The above separation processes are complex in many cases, involving a number of stages, and obviously require expenditure of funds in their implementation. It may also be noted that, in many of these approaches, only one useable product is obtained from the separation process, and there still remains the problem of disposing of the other residues from the production process.
Analysis of post consumer carpet face yarn has indicated that a variety of contaminants may be present depending upon the exposure of the carpet during its lifetime. Undesirable contaminants that may need to be removed so that the reclaimed face yarn can be reused in a fiber spinning process include but are not limited to, sand, cellulose (for example in the form of wood or paper), latex, rubber, carpet backing materials, gypsum and other construction materials. Other possible contaminants include animal hair from pets, humans and textile fabrics, and vegetable matter. All of these contaminants are typically solids of very large “particle” sizes in comparison to the size of individual carpet yarn filaments. These contaminants need to be removed before the reclaimed material is suitable for fiber spinning, particularly those contaminants that do not melt at the fiber extrusion temperatures of the polymer being recycled, or are incompatible with the polymer being recycled. Melt extrusion fiber spinning methods typically incorporate fine filtration as part of the process so that large particle contaminants are excluded from the formed fibers. The presence of large particle contaminants reduces the strength of the formed fibers, making them unsuitable for most carpet or textile applications. In addition, high levels of contaminants, particularly of large particle size, result in short extruder filter life such that the fiber spinning process is uneconomical due to the need for very frequent filter screen changes.
Prior to this invention there has been no method suitable for reclaiming and reuse of carpet face yarn suitable for using in a melt extrusion fiber spinning to produce carpet or textile yarns without use of the undesirable depolymerization and repolymerization methods.
Methods have been discovered of producing post consumer carpet yarn reclaim of sufficient cleanliness that the reclaimed product can then be economically used for further carpet yarn production without detrimental loss of physical properties of the yarn produced.